Memory arrays, and methods of forming memory arrays

ABSTRACT

Some embodiments include a memory array having a vertical stack of alternating insulative levels and wordline levels. Channel material extends along the stack. Conductive segments are along the wordline levels. Each of the conductive segments has, along a cross-section, first and second ends in opposing relation to one another. The conductive segments include gates and wordlines adjacent the gates. The wordlines encompass the second ends, and the gates have rounded (e.g., substantially parabolic) noses which encompass the first ends. Some embodiments include methods of forming integrated assemblies.

RELATED PATENT DATA

This patent resulted from a continuation of U.S. patent application Ser.No. 16/987,187 filed Aug. 6, 2020, which is a divisional of U.S. patentapplication Ser. No. 16/177,220 filed Oct. 31, 2018, which is herebyincorporated by reference herein.

TECHNICAL FIELD

Memory arrays (e.g., NAND memory arrays), and methods of forming memoryarrays.

BACKGROUND

Memory provides data storage for electronic systems. Flash memory is onetype of memory, and has numerous uses in modern computers and devices.For instance, modern personal computers may have BIOS stored on a flashmemory chip. As another example, it is becoming increasingly common forcomputers and other devices to utilize flash memory in solid statedrives to replace conventional hard drives. As yet another example,flash memory is popular in wireless electronic devices because itenables manufacturers to support new communication protocols as theybecome standardized, and to provide the ability to remotely upgrade thedevices for enhanced features.

NAND may be a basic architecture of flash memory, and may be configuredto comprise vertically-stacked memory cells.

Before describing NAND specifically, it may be helpful to more generallydescribe the relationship of a memory array within an integratedarrangement. FIG. 1 shows a block diagram of a prior art device 1000which includes a memory array 1002 having a plurality of memory cells1003 arranged in rows and columns along with access lines 1004 (e.g.,wordlines to conduct signals WL0 through WLm) and first data lines 1006(e.g., bitlines to conduct signals BL0 through BLn). Access lines 1004and first data lines 1006 may be used to transfer information to andfrom the memory cells 1003. A row decoder 1007 and a column decoder 1008decode address signals AO through AX on address lines 1009 to determinewhich ones of the memory cells 1003 are to be accessed. A senseamplifier circuit 1015 operates to determine the values of informationread from the memory cells 1003. An I/O circuit 1017 transfers values ofinformation between the memory array 1002 and input/output (I/O) lines1005. Signals DQ0 through DQN on the I/O lines 1005 can represent valuesof information read from or to be written into the memory cells 1003.Other devices can communicate with the device 1000 through the I/O lines1005, the address lines 1009, or the control lines 1020. A memorycontrol unit 1018 is used to control memory operations to be performedon the memory cells 1003, and utilizes signals on the control lines1020. The device 1000 can receive supply voltage signals Vcc and Vss ona first supply line 1030 and a second supply line 1032, respectively.The device 1000 includes a select circuit 1040 and an input/output (I/O)circuit 1017. The select circuit 1040 can respond, via the I/O circuit1017, to signals CSEL1 through CSELn to select signals on the first datalines 1006 and the second data lines 1013 that can represent the valuesof information to be read from or to be programmed into the memory cells1003. The column decoder 1008 can selectively activate the CSEL1 throughCSELn signals based on the AO through AX address signals on the addresslines 1009. The select circuit 1040 can select the signals on the firstdata lines 1006 and the second data lines 1013 to provide communicationbetween the memory array 1002 and the I/O circuit 1017 during read andprogramming operations.

The memory array 1002 of FIG. 1 may be a NAND memory array, and FIG. 2shows a block diagram of a three-dimensional NAND memory device 200which may be utilized for the memory array 1002 of FIG. 1 . The device200 comprises a plurality of strings of charge-storage devices. In afirst direction (Z-Z′), each string of charge-storage devices maycomprise, for example, thirty-two charge-storage devices stacked overone another with each charge-storage device corresponding to one of, forexample, thirty-two tiers (e.g., Tier0-Tier31). The charge-storagedevices of a respective string may share a common channel region, suchas one formed in a respective pillar of semiconductor material (e.g.,polysilicon) about which the string of charge-storage devices is formed.In a second direction (X-X′), each first group of, for example, sixteenfirst groups of the plurality of strings may comprise, for example,eight strings sharing a plurality (e.g., thirty-two) of access lines(i.e., “global control gate (CG) lines”, also known as wordlines, WLs).Each of the access lines may couple the charge-storage devices within atier. The charge-storage devices coupled by the same access line (andthus corresponding to the same tier) may be logically grouped into, forexample, two pages, such as P0/P32, P1/P33, P2/P34 and so on, when eachcharge-storage device comprises a cell capable of storing two bits ofinformation. In a third direction (Y-Y′), each second group of, forexample, eight second groups of the plurality of strings, may comprisesixteen strings coupled by a corresponding one of eight data lines. Thesize of a memory block may comprise 1,024 pages and total about 16 MB(e.g., 16 WLs×32 tiers×2 bits=1,024 pages/block, block size=1,024pages×16 KB/page=16 MB). The number of the strings, tiers, access lines,data lines, first groups, second groups and/or pages may be greater orsmaller than those shown in FIG. 2 .

FIG. 3 shows a cross-sectional view of a memory block 300 of the 3D NANDmemory device 200 of FIG. 2 in an X-X′ direction, including fifteenstrings of charge-storage devices in one of the sixteen first groups ofstrings described with respect to FIG. 2 . The plurality of strings ofthe memory block 300 may be grouped into a plurality of subsets 310,320, 330 (e.g., tile columns), such as tile column_(I), tile column_(j)and tile column_(K), with each subset (e.g., tile column) comprising a“partial block” of the memory block 300. A global drain-side select gate(SGD) line 340 may be coupled to the SGDs of the plurality of strings.For example, the global SGD line 340 may be coupled to a plurality(e.g., three) of sub-SGD lines 342, 344, 346 with each sub-SGD linecorresponding to a respective subset (e.g., tile column), via acorresponding one of a plurality (e.g., three) of sub-SGD drivers 332,334, 336. Each of the sub-SGD drivers 332, 334, 336 may concurrentlycouple or cut off the SGDs of the strings of a corresponding partialblock (e.g., tile column) independently of those of other partialblocks. A global source-side select gate (SGS) line 360 may be coupledto the SGSs of the plurality of strings. For example, the global SGSline 360 may be coupled to a plurality of sub-SGS lines 362, 364, 366with each sub-SGS line corresponding to the respective subset (e.g.,tile column), via a corresponding one of a plurality of sub-SGS drivers322, 324, 326. Each of the sub-SGS drivers 322, 324, 326 mayconcurrently couple or cut off the SGSs of the strings of acorresponding partial block (e.g., tile column) independently of thoseof other partial blocks. A global access line (e.g., a global CG line)350 may couple the charge-storage devices corresponding to therespective tier of each of the plurality of strings. Each global CG line(e.g., the global CG line 350) may be coupled to a plurality ofsub-access lines (e.g., sub-CG lines) 352, 354, 356 via a correspondingone of a plurality of sub-string drivers 312, 314 and 316. Each of thesub-string drivers may concurrently couple or cut off the charge-storagedevices corresponding to the respective partial block and/or tierindependently of those of other partial blocks and/or other tiers. Thecharge-storage devices corresponding to the respective subset (e.g.,partial block) and the respective tier may comprise a “partial tier”(e.g., a single “tile”) of charge-storage devices. The stringscorresponding to the respective subset (e.g., partial block) may becoupled to a corresponding one of sub-sources 372, 374 and 376 (e.g.,“tile source”) with each sub-source being coupled to a respective powersource.

The NAND memory device 200 is alternatively described with reference toa schematic illustration of FIG. 4 .

The memory array 200 includes wordlines 202 ₁ to 202 _(N), and bitlines228 ₁ to 228 _(M).

The memory array 200 also includes NAND strings 206 ₁ to 206 _(M). EachNAND string includes charge-storage transistors 208 ₁ to 208 _(N). Thecharge-storage transistors may use floating gate material (e.g.,polysilicon) to store charge, or may use charge-trapping material (suchas, for example, silicon nitride, metallic nanodots, etc.) to storecharge.

The charge-storage transistors 208 are located at intersections ofwordlines 202 and strings 206. The charge-storage transistors 208represent non-volatile memory cells for storage of data. Thecharge-storage transistors 208 of each NAND string 206 are connected inseries source-to-drain between a source-select device (e.g., source-sideselect gate, SGS) 210 and a drain-select device (e.g., drain-side selectgate, SGD) 212. Each source-select device 210 is located at anintersection of a string 206 and a source-select line 214, while eachdrain-select device 212 is located at an intersection of a string 206and a drain-select line 215. The select devices 210 and 212 may be anysuitable access devices, and are generically illustrated with boxes inFIG. 4 .

A source of each source-select device 210 is connected to a commonsource line 216. The drain of each source-select device 210 is connectedto the source of the first charge-storage transistor 208 of thecorresponding NAND string 206. For example, the drain of source-selectdevice 210 ₁ is connected to the source of charge-storage transistor 208₁ of the corresponding NAND string 206 ₁. The source-select devices 210are connected to source-select line 214.

The drain of each drain-select device 212 is connected to a bitline(i.e., digit line) 228 at a drain contact. For example, the drain ofdrain-select device 212 ₁ is connected to the bitline 228 ₁. The sourceof each drain-select device 212 is connected to the drain of the lastcharge-storage transistor 208 of the corresponding NAND string 206. Forexample, the source of drain-select device 212 ₁ is connected to thedrain of charge-storage transistor 208 _(N) of the corresponding NANDstring 206 ₁.

The charge-storage transistors 208 include a source 230, a drain 232, acharge-storage region 234, and a control gate 236. The charge-storagetransistors 208 have their control gates 236 coupled to a wordline 202.A column of the charge-storage transistors 208 are those transistorswithin a NAND string 206 coupled to a given bitline 228. A row of thecharge-storage transistors 208 are those transistors commonly coupled toa given wordline 202.

It would be desirable to develop improved memory cell designs, improvedmemory array architecture (e.g., improved NAND architecture), andmethods for fabricating the improved memory cells and improved memoryarray architectures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of a prior art memory device having amemory array with memory cells.

FIG. 2 shows a schematic diagram of the prior art memory array of FIG. 1in the form of a 3D NAND memory device.

FIG. 3 shows a cross-sectional view of the prior art 3D NAND memorydevice of FIG. 2 in an X-X′ direction.

FIG. 4 is a schematic diagram of a prior art NAND memory array.

FIGS. 5-14 are diagrammatic cross-sectional views of regions of aconstruction at example process steps of an example method forfabricating an example assembly.

FIG. 6A is diagrammatic top view along the line A-A of FIG. 6 .

FIGS. 15-19 are diagrammatic cross-sectional views of regions of aconstruction at example process steps of an example method forfabricating an example assembly. The processing stage of FIG. 15 mayfollow that of FIG. 6 .

FIGS. 20-22 are diagrammatic cross-sectional views of regions of aconstruction at example process steps of an example method forfabricating an example assembly. The processing stage of FIG. 20 mayfollow that of FIG. 17 .

FIGS. 23-26 are diagrammatic cross-sectional views of regions of aconstruction at example process steps of an example method forfabricating an example assembly. The processing stage of FIG. 23 mayfollow that of FIG. 21 .

FIGS. 27A and 27B are diagrammatic cross-sectional views of regions ofexample constructions showing advantages of a rounded-nose-shaped (e.g.,parabolic-shaped) gate (FIG. 27B) relative to a non-rounded-nose-shapedgate (FIG. 27A).

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Some embodiments include memory arrays (e.g., NAND memory arrays) havingvertically-stacked conductive segments. The conductive segments havefirst and second ends in opposing relation to one another. Wordlinesencompass the second ends, and transistor gates encompass the firstends. The transistor gates may have rounded noses (e.g., substantiallyparabolic noses). Channel material extends vertically along thevertically-stacked conductive segments. The rounded noses are spacedfrom the channel material by memory cell structures which includedielectric barrier material, charge-blocking material, andcharge-storage material. Some embodiments include methods of formingintegrated assemblies. Example methods are described with reference toFIGS. 5-26, 27A and 27B.

Referring to FIG. 5 , a construction (i.e., assembly, architecture,etc.) 10 includes a stack 12 of alternating first and second levels 14and 16. The first levels 14 comprise first material 18, and the secondlevels 16 comprise second material 20. The first and second materials 18and 20 may be any suitable materials. In some embodiments, the firstmaterial 18 may comprise, consist essentially of, or consist of siliconnitride; and the second material 20 may comprise, consist essentiallyof, or consist of silicon dioxide. The second material 20 may beelectrically insulative, and in some embodiments may be referred to asan insulative second material.

The levels 14 and 16 may be of any suitable thicknesses; and may be thesame thickness as one another, or different thicknesses relative to oneanother. In some embodiments, the levels 14 and 16 may have verticalthicknesses within a range of from about 3 nanometers (nm) to about 400nm; within a range of from about 3 nm to about 50 nm, etc.

In some embodiments, the second levels 16 may be thinner than the firstlevels 14. In an example embodiment, the second levels 16 may havethicknesses of about 7 nm, and the first levels 14 may have thicknessesof about 9 nm. In other embodiments, the second levels 16 may be thickerthan the first levels 14.

Some of the material 18 of the first levels 14 is ultimately replacedwith conductive material of memory cell gates. Accordingly, the levels14 may ultimately correspond to memory cell levels of a NANDconfiguration. The NAND configuration will include strings of memorycells (i.e., NAND strings), with the number of memory cells in thestrings being determined by the number of vertically-stacked levels 14.The NAND strings may comprise any suitable number of memory cell levels.For instance, the NAND strings may have 8 memory cell levels, 16 andmemory cell levels, 32 memory cell levels, 64 memory cell levels, 512memory cell levels, 1024 memory cell levels, etc. The vertical stack 12is shown to extend outwardly beyond the illustrated region of the stackto indicate that there may be more vertically-stacked levels than thosespecifically illustrated in the diagram of FIG. 5 .

The stack 12 is shown to be supported over a base 22. The base 22 maycomprise semiconductor material; and may, for example, comprise, consistessentially of, or consist of monocrystalline silicon. The base 22 maybe referred to as a semiconductor substrate. The term “semiconductorsubstrate” means any construction comprising semiconductive material,including, but not limited to, bulk semiconductive materials such as asemiconductive wafer (either alone or in assemblies comprising othermaterials), and semiconductive material layers (either alone or inassemblies comprising other materials). The term “substrate” refers toany supporting structure, including, but not limited to, thesemiconductor substrates described above. In some applications, the base22 may correspond to a semiconductor substrate containing one or morematerials associated with integrated circuit fabrication. Such materialsmay include, for example, one or more of refractory metal materials,barrier materials, diffusion materials, insulator materials, etc.

A space is provided between the stack 12 and the base 22 to indicatethat other components and materials may be provided between the stack 12and the base 22. Such other components and materials may compriseadditional levels of the stack, a source line level, source-side selectgates (SGSs), etc.

Referring to FIG. 6 , an opening 24 is formed through the stack 12. Theopening is ultimately utilized for fabricating channel material pillarsassociated with vertically-stacked memory cells of a memory array, andin some embodiments may be referred to as a pillar opening. The opening24 may have any suitable configuration when viewed from above; and insome example embodiments may be circular, elliptical, polygonal, etc.FIG. 6A shows a top view of a portion of the top level 14 of theillustrated region of construction 10, and illustrates an exampleconfiguration in which the opening 24 is circular-shaped when viewedfrom above. In some embodiments, the opening 24 may be referred to as afirst opening in order to distinguish it from other openings formed atlater process stages. The pillar opening 24 may be representative of alarge plurality of substantially identical openings formed across thebase 22 at the processing stage of FIG. 6 (with the term “substantiallyidentical” meaning identical to within reasonable tolerances offabrication and measurement).

The first levels 14 comprise edges 19 along the opening 24, and thesecond levels 16 comprise edges 21 along the opening. The edges 19 and21 may be referred to as first and second edges, respectively; andtogether form sidewalls 23 along the opening 24.

Referring to FIG. 7 , the edges 21 of the second levels 16 are recessedwith an appropriate etch. For instance, if the second material 20comprises silicon dioxide, the edges 21 may be recessed with an etchutilizing hydrofluoric acid (HF), such as, for example, a buffered oxideetch or a vapor etch.

The etch utilized to recess the edges 21 of the second levels 16 alsorounds the edges 19 of the first levels 14.

The recessing of the edges 21 insets such edges to leave recesses 26between vertically-adjacent rounded edges of the first levels 14.

In some embodiments, the second levels 16 may be considered to havevertical thicknesses of a first dimension D₁, and the recesses 26 maydepths (specifically, horizontal depths) of a second dimension D₂. Thesecond dimension D₂ may be at least about 10% of the first dimension D₁,at least about 20% of the first dimension D₁, at least about 40% of thefirst dimension D₁, at least about 60% of the first dimension D₁, etc.In some embodiments, the second dimension D₂ is at least about one-halfof the first dimension D₁. For instance, the first dimension D₁ may beabout 9 nm, and the second dimension D₂ may be at least about 5 nm.

In some embodiments, the edges 19 and 21 may be referred to as first andsecond edges, respectively.

Referring to FIG. 8 , the rounded edges 19 (FIG. 7 ) of material 18 areoxidized to form a material 28 comprising silicon, nitrogen and oxygen.In some embodiments, the material 28 may comprise, consist essentiallyof, or consist of silicon oxynitride. The material 28 along each of thelevels 14 has an inner edge (i.e., inner surface) 29. The inner edges 29are rounded, and may be conformal to the rounded edges 19 (FIG. 7 )formed along the first levels 14. In some embodiments, the inner edges29 may be considered to comprise rounded shapes patterned by the roundedshapes of the edges 19 (FIG. 7 ).

The oxidation of material 18 may utilize any suitable chemistry andoperational parameters. In some example embodiments, the oxidation maycomprise an operational temperature of the ambient adjacent theoxidizing surfaces and/or the operational temperature of the oxidizingsurfaces of at least about 700° C. (but not limited to being at leastabout 700°, and may be lower if suitable oxidative conditions achievedesired electrical and/or other properties). The oxidation may, forexample, utilize steam (for instance, in situ steam generation (ISSG))as a source of the oxidant, and/or may utilize plasma to generateoxidizing species. The plasma may be a so-called “remote plasma”,meaning that the plasma does not contact the surfaces within opening 24which are to be oxidized, but instead only the oxidizing speciesgenerated by such plasma reach the oxidizing surfaces.

The material 28 may correspond to charge-blocking material in someembodiments. Such charge-blocking material may be formed to any suitablehorizontal thickness; such as, for example, a horizontal thicknesswithin a range of from about 5 nm to about 15 nm.

Referring to FIG. 9 , charge-storage material 30 is formed adjacent thecharge-blocking material 28, and in the shown embodiment is formed to bedirectly against the charge-blocking material 28. The charge-storagematerial may comprise any suitable composition(s); and in someembodiments may comprise charge-trapping materials, such as siliconnitride, silicon oxynitride, conductive nanodots, etc. Persons ofordinary skill understand the term “charge-trapping”; and willunderstand that a “charge trap” may refer to an energy well that canreversibly capture a charge carrier (e.g., an electron or hole). Inalternative embodiments (not shown), the charge-storage material may beconfigured as floating gate material (such as, for example,polycrystalline silicon). In some embodiments, the charge-trappingmaterial 30 may comprise, consist essentially of, or consist of siliconnitride.

Referring to FIG. 10 , tunneling structures 32 are formed adjacent thecharge-trapping material 30, and in the shown embodiment are formed tobe directly against the charge-trapping material 30.

The tunneling structures 32 comprise tunneling materials 34, 36 and 38.The tunneling materials can function as materials through which chargecarriers tunnel or otherwise pass during programming operations, erasingoperations, etc. In some contexts, one or more of the tunnelingmaterials may be referred to as gate dielectric material, or simply asdielectric material. In the illustrated embodiment, three tunnelingmaterials are utilized. In other embodiments, there may be fewer thanthree tunneling materials; and in yet other embodiments there may bemore than three tunneling materials. In some embodiments, the tunnelingmaterials 34, 36 and 38 may be band-gap engineered to have desiredcharge-tunneling properties. The tunneling material 36 iscompositionally different from the materials 34 and 38. The materials 34and 38 may be compositionally different from one another in someembodiments, and may be compositionally the same as one another in otherembodiments.

In some example embodiments, the tunneling material 36 may comprisesilicon nitride, and the tunneling materials 34 and 38 may comprisesilicon dioxide.

In some embodiments, the tunneling materials 34, 36 and 38 may bereferred to as first, second and third tunneling materials,respectively.

Channel material 40 is formed within the opening 24 and along thetunneling materials 34, 36 and 38. In the illustrated embodiment, thechannel material 40 is directly against the tunneling material 38. Thechannel material 40 may comprise any suitable appropriately-dopedsemiconductor material(s); and in some embodiments may comprise one ormore of silicon, germanium, III/V semiconductor materials (e.g., galliumphosphide), etc., (with groups III and V being old nomenclature, and nowbeing referred to as groups 13 and 15)

In the illustrated embodiment, the channel material 40 lines a peripheryof the opening 24, and insulative material 42 fills a remaining interiorregion of the opening 24. The insulative material 42 may comprise anysuitable composition or combination of compositions, such as, forexample, silicon dioxide. The illustrated configuration of the channelmaterial 40 may be considered to be a hollow channel configuration, inthat the insulative material 42 is provided within a “hollow” in thechannel configuration. In other embodiments, the channel material may beconfigured as a solid pillar.

The channel material 40 extends vertically along the periphery ofopening 24; or, in other words, extends vertically through the stack 12.

Referring to FIG. 11 , second openings 44 (e.g., slits) are formedthrough the stack 12.

Referring to FIG. 12 , the first material 18 (FIG. 11 ) of the firstlevels 14 is removed to form cavities 46 along the first levels 14. Thecavities 46 have peripheral edges which include the inner edges 29 ofthe charge-blocking material 28.

Referring to FIG. 13 , dielectric barrier material 48 is formed withinthe cavities 46; and conductive materials 50 and 52 are provided withinthe lined cavities.

The dielectric barrier material 48 may comprise any suitablecomposition(s); and in some embodiments may comprise one or more high-kmaterials (with the term high-k meaning a dielectric constant greaterthan that of silicon dioxide). Example compositions which may beincorporated into the dielectric barrier material are hafnium oxide,zirconium oxide, aluminum oxide, hafnium silicate, zirconium silicate,titanium oxide, gadolinium oxide, niobium oxide, tantalum oxide, etc.

The conductive materials 50 and 52 may comprise any suitableelectrically conductive composition(s), such as, for example, one ormore of various metals (e.g., titanium, tungsten, cobalt, nickel,platinum, ruthenium, etc.), metal-containing compositions (e.g., metalsilicide, metal nitride, metal carbide, etc.), and/or conductively-dopedsemiconductor materials (e.g., conductively-doped silicon,conductively-doped germanium, etc.). In some embodiments, the conductivematerial 50 may comprise, consist essentially of, or consist of titaniumnitride; and the conductive material 52 may comprise, consistessentially of, or consist of tungsten.

Referring to FIG. 14 , conductive materials 50 and 52 are removed fromwithin central regions of openings 44, while leaving the conductivematerials 50 and 52 within the cavities 46.

The conductive materials 50 and 52 remaining within the cavities 46together form conductive segments (or regions) 54. Although theillustrated conductive segments 54 comprise two conductive materials, inother embodiments analogous conductive regions may comprise only asingle conductive material, or may comprise more than two conductivematerials.

Portions of the conductive segments 54 proximate the charge-blockingmaterial 28 may correspond to conductive gates 56, and portions of theconductive segments 54 more distal from the charge-blocking material 28may correspond to wordlines 58. The wordlines are along the levels 14,and accordingly in some embodiments the levels 14 may be referred to aswordline levels. Such wordline levels may be considered to alternatewith the insulative levels 16 within the vertical stack 12 of FIG. 14 .

In some embodiments, the conductive segments 54 may be considered tocomprise first ends 55, and to comprise second ends 57 in opposingrelation to the first ends (at least along the cross-section of FIG. 14). The first ends 55 are comprised by the gates 56, and may be referredto as gate ends; and the second ends 57 are comprised by the wordlines58, and may be referred to as wordline ends.

The gate ends 55 are rounded, and specifically are patterned by therounded inner edges 29 of the charge-blocking material 28. In someembodiments, the gate ends 55 may be considered to have a rounded shapemolded by the rounded inner edges 29 of the charge-blocking material 28.As discussed above with reference to FIG. 8 , the inner edges 29 may beconsidered to be patterned by the rounded edges 19 shown in FIG. 7 .Since the rounded ends 55 have been patterned by the inner edges 29, insome embodiments such rounded ends may be considered to be patternedfrom a shape initially provided as the rounded edges 19 of FIG. 7 .

In some embodiments, the gates 56 may be considered to comprise roundednoses 60 which encompass the first ends 55. Such rounded noses may haveany suitable shapes, and in some embodiments may have substantiallyparabolic shapes (with the term “substantially parabolic” meaningparabolic to within reasonable tolerances of fabrication andmeasurement).

The assembly 10 of FIG. 14 may be considered to show a portion of amemory array (e.g., a NAND memory array). Such array comprises thevertical stack 12 of alternating insulative levels 16 and wordlinelevels 14. The channel material 40 extends vertically along the stack12. The conductive segments 54 are along the wordline levels 14.

The memory array includes memory cells 62 a, 62 b and 62 c. Thecharge-blocking material 28 and the charge-storage material 30 within amemory cell may be together considered to be a memory cell structure 64.In some embodiments, the charge-blocking material 28 within a memorycell structure 64 may be referred to as a charge-blocking region of thememory cell structure, and the charge-storage material within the memorycell structure 64 may be referred to as a charge-storage region of thememory cell structure. In the shown embodiment, the charge-blockingregions (i.e., the regions of material 28) are between thecharge-storage regions (i.e., the regions of material 30) and the gates56.

The dielectric barrier material 48 is between the charge-blockingmaterial 28 and the noses 60 of the gates 56. In the shown embodiment,the dielectric barrier material is substantially conformal to therounded noses 60 (with the term “substantially conformal” meaningconformal to within reasonable tolerances of fabrication andmeasurement).

In operation, the charge-storage material 30 may be configured to storeinformation in the memory cells 62 a, 62 b and 62 c. The value (with theterm “value” representing one bit or multiple bits) of informationstored in an individual memory cell (e.g., 62 a) may be based on theamount of charge (e.g., the number of electrons) stored in acharge-storage region. The amount of charge within an individualcharge-storage region may be controlled (e.g., increased or decreased),at least in part, based on the value of voltage applied to an associatedgate 56, and/or based on the value of voltage applied to an associatedchannel material 40.

The tunneling structures 32 may be configured to allow desired tunneling(e.g., transportation) of charge (e.g., electrons) between thecharge-storage material 30 and the channel material 40. The tunnelingstructures 32 may be configured (i.e., engineered) to achieve a selectedcriterion, such as, for example, but not limited to, an equivalent oxidethickness (EOT). The EOT quantifies the electrical properties of thetunneling region (e.g., capacitance) in terms of a representativephysical thickness. For example, EOT may be defined as the thickness ofa theoretical silicon dioxide layer that would be required to have thesame capacitance density as a given dielectric (e.g., a tunnelingstructure 32), ignoring leakage current and reliability considerations.

The charge-blocking material 28 is adjacent to the charge-storagematerial 30, and may provide a mechanism to block charge from flowingfrom the charge-storage material 30 to the associated gates 56. Thedielectric barrier material 48 is provided between the charge-blockingmaterial 28 and the associated gates 56, and may be utilized to inhibitback-tunneling of electrons from the gates 56 toward the charge-storagematerial 30. In some embodiments, the dielectric barrier material 48 maybe considered to form dielectric barrier regions within the memory cells62 a, 62 b and 62 c.

Although the embodiment of FIGS. 7-14 forms the entirety of thecharge-blocking material 28 as oxidized regions of the first material 18(as shown in FIG. 8 ), in other embodiments regions of thecharge-blocking material may be formed by depositing a charge-blockingcomposition over the rounded surfaces 19, or onto the charge-blockingmaterial 28. The deposited charge-blocking composition may comprise anysuitable substance(s); such as, for example, silicon dioxide.

The embodiment of FIGS. 7-14 forms the dielectric barrier material 48within the cavities 46 (FIG. 12 ), and conformally to the rounded noses60 of the gates 56 (FIG. 14 ). In other embodiments, the dielectricbarrier material 48 may be formed in other locations. An example of suchother embodiments is described with reference to FIGS. 15-19 .

Referring to FIG. 15 , the construction 10 is shown at a processingstage subsequent to that of FIG. 6 and analogous to that of FIG. 7 .

Referring to FIG. 16 , insulative material 66 is formed within theopening 24 and along the edges 19 and 21 of the first and secondmaterials 18 and 20. In some embodiments, the material 66 may bereferred to as an insulative third material to distinguish it from otherinsulative materials.

The material 66 extends into the recesses 26. The material 66 maycomprise any suitable composition(s), and in some embodiments maycomprise, consist essentially of, or consist of silicon dioxide.

The material 66 may be formed to any suitable horizontal thickness; andin some embodiments may be formed to a horizontal thickness within arange of from about 10 nm to about 15 nm.

Referring to FIG. 17 , the material 66 is etched to remove the material66 from along regions of the rounded edges 19 which leaving the material66 within the recesses 26. Such etching may utilize any suitableconditions. In some embodiments, the material 66 comprises silicondioxide and the etching may utilize HF (e.g., buffered oxide etchingconditions, vapor etching conditions, etc.).

In the shown embodiment, the etching of material 66 forms substantiallyvertical surfaces 67 along the interior of opening 24; with suchsubstantially vertical surfaces 67 including regions of the surfaces 19of the first material 18, and regions of the remaining surfaces ofmaterial 66. The term “substantially vertical” means vertical to withinreasonable tolerances of fabrication and measurement.

Referring to FIG. 18 , the charge-blocking material 28 is formed alongthe surfaces 67, the charge-storage material 30 is formed adjacent thecharge-blocking material, the tunneling structures 32 are formedadjacent the charge-trapping material, and the channel material 40 isformed adjacent the tunneling structures. In the illustrated embodiment,the channel material 40 lines a periphery of the opening 24, and theinsulative material 42 fills a remaining interior region of the opening24.

In the embodiment of FIG. 18 , the charge-blocking material may, forexample, comprise, consist essentially of, or consist of one or both ofsilicon dioxide and silicon oxynitride.

Referring to FIG. 19 , the construction 10 of FIG. 18 is shown afterbeing subjected to processing analogous to that described above withreference to FIGS. 12-14 . The construction includes the dielectricbarrier material 48. The construction also includes the conductivesegments (or regions) 54 comprising the conductive materials 50 and 52.The conductive segments 54 comprise the portions corresponding toconductive gates 56 having first ends 55, and comprise the portionscorresponding to the wordlines 58 having second ends 57. The gate ends55 are rounded, and specifically are patterned by the rounded edges 19shown in FIG. 15 . Accordingly, the gates 56 comprise the rounded noses60. Such rounded noses may have any suitable shapes, and in someembodiments may have substantially parabolic shapes.

The assembly 10 of FIG. 19 may be considered to show a portion of amemory array (e.g., a NAND memory array). Such array comprises thevertical stack 12 of alternating insulative levels 16 and wordlinelevels 14.

The memory array includes memory cells 62 a, 62 b and 62 c. Thecharge-blocking material 28 and charge-storage material 30 within amemory cell may be together considered to be the memory cell structure64. As discussed above, the charge-blocking material 28 within thememory cell structure 64 may be referred to as the charge-blockingregion of the memory cell structure, and the charge-storage materialwithin the memory cell structure may be referred to as thecharge-storage region of the memory cell structure. In the shownembodiment the charge-blocking material 28 is configured as avertically-extending layer which extends substantially conformally tothe channel material 40, and the charge-blocking regions are along suchvertically-extending layer.

In some embodiments, the dielectric barrier material 48 may be formedalong the surface 67 (FIG. 17 ) in addition to, or alternatively to,being formed within the cavities 46 (FIG. 12 ). FIG. 20 showsconstruction 10 at a processing stage following that of FIG. 17 . Thedielectric barrier material 48 is formed as vertically-extending layersalong the surfaces 67, and the charge-blocking material 28 is formedalong the dielectric barrier material 48.

Referring to FIG. 21 , the charge-storage material 30 is formed adjacentthe charge-blocking material 28, the tunneling structures 32 are formedadjacent the charge-trapping material, and the channel material 40 isformed adjacent the tunneling structures. In the illustrated embodiment,the channel material 40 lines a periphery of the opening 24, and theinsulative material 42 fills a remaining interior region of the opening24.

Referring to FIG. 22 , the construction 10 of FIG. 21 is shown afterbeing subjected to processing analogous to that described above withreference to FIGS. 12-14 . The construction includes the conductivesegments (or regions) 54 comprising the conductive materials 50 and 52.The conductive segments 54 comprise the portions corresponding toconductive gates 56 having first ends 55, and comprise the portionscorresponding to the wordlines 58 having second ends 57.

The memory array includes memory cells 62 a, 62 b and 62 c. In the shownembodiment, the channel material 40 extends vertically along thevertically-stacked memory cells 62 a, 62 b and 62 c. The charge-blockingmaterial 28 is configured as a layer which extends substantiallyconformally to the channel material 40, and the dielectric barriermaterial 48 is configured as a layer which extends substantiallyconformally to the layer of the charge-blocking material 28.

In some embodiments, the shapes of the cavities 46 (FIG. 12 ) may bemodified. FIG. 23 shows a processing stage subsequent to that of FIG. 21, and shows the material 18 removed to form the cavities 46. The regionsof material 20 between the cavities may be considered to be insulativesegments 68. Dashed lines 69 are provided to show initial peripheries ofthe segments 20 (e.g., peripheries at a process stage analogous to thatof FIG. 12 ). Each of the cavities has an upper portion bounded by abottom surface 71 of an insulative segment 68, and has a lower portionbounded by an upper surface 73 of an insulative segment 68. The surfaces71 and 73 are illustrated as being surfaces 71 a and 73 a along theinitial peripheries (i.e., the dashed-line peripheries) The processingstage of FIG. 23 shows construction 10 after etching is conducted tomodify the cavities 46. Such etching etches into the surfaces of thesegments 68. The etching drops regions of the upper surfaces 73 of thesegments 68 to new positions labeled 73 b, and raises regions of thelower surfaces 71 of such segments to new positions labeled 71 b; andthereby widens regions of the cavities 46 proximate the slits 44.

Referring to FIG. 24 , the construction 10 of FIG. 23 is shown at aprocessing stage analogous to that described above with reference toFIG. 22 . The construction includes the conductive segments (or regions)54 comprising the conductive materials 50 and 52. The conductivesegments 54 comprise the portions corresponding to conductive gates 56having first ends 55, and comprise the portions corresponding to thewordlines 58 having second ends 57. An advantage of the construction ofFIG. 24 relative to that of FIG. 22 is that the wordlines 58 of the FIG.24 construction are thicker than those of the FIG. 22 construction. Suchmay enable the wordlines to have reduced resistance (i.e., increasedconductance) as compared to the wordlines of the embodiment of FIG. 22 .

In some embodiments, it may be desired to replace at least some of theinsulative material 20 with voids in order to reduce a dielectricconstant of regions between vertically-neighboring conductive structuresand thereby reduce undesired parasitic capacitance. FIG. 25 showsconstruction 10 at a processing stage which may follow that of FIG. 24 .The insulative material 20 (FIG. 24 ) has been removed with one or moresuitable etches to form voids 70. Such voids 70 are between regions ofvertically-adjacent conductive segments 54.

Referring to FIG. 26 , insulative liners 72 may be formed along theslits 44. The insulative liners comprise insulative material 74. Suchinsulative material may comprise any suitable composition(s); such as,for example, silicon dioxide or low-k silicon dioxide (with the termlow-k meaning a dielectric constant less than that of traditionalsilicon dioxide). Low-k silicon dioxide may be silicon dioxide which ismore porous than traditional silicon dioxide. The liner material sealsthe voids 70, and in some embodiments may extend partially into thevoids 70 (as shown). In some embodiments, the insulative liners 72 maybe considered to comprise liner regions 76 which extend around thesecond ends 57 of the conductive segments 54 and into the voids 70.

The embodiments described above have the charge-storage material 30extending continuously along the wordlines levels 14 and the insulativelevels 16. In other embodiments, the charge-storage material may beconfigured as segments along the wordline levels 14, withvertically-neighboring segments being spaced from one another by breaksalong the insulative levels 16. Such may advantageously reducecross-coupling between vertically-adjacent memory cells in someapplications.

The embodiments described herein may advantageously enable improvedcontrol over charge-trapping as compared to conventional memory cellconfigurations, and may reduce disturbance between vertically-adjacentmemory cells as compared to conventional configurations. Such may enablefaster programming speeds and improved retention as compared toconventional configurations. FIGS. 27A and 27B compare a conventionalconfiguration 100 with a configuration 150 representative of anembodiment of the present invention. The configuration 100 comprises agate 56 a having a nose 60 a with a square-shaped configuration. Incontrast, the configuration 150 comprises a gate 56 b having a nose 60 bwith a rounded (e.g., parabolic) configuration. The gate 56 b betterconcentrates an electric field (indicated with dashed lines) that passesacross charge-storage material 30 and channel material 40, as comparedto the gate 56 a; and specifically the electric field of theconventional configuration 100 is dispersed across a distance D₃, whilea comparable electric field of the configuration 150 is concentratedwithin a smaller distance D₄. The improved concentration of the electricfield achieved with embodiments described herein may advantageouslyenable the electric field to be enhanced within a small region of thecharge-storage material, leading to faster programming. The improvedconcentration of the electric field may also advantageously reduce thelikelihood of cross-coupling between vertically-adjacent memory cells ascompared to conventional memory cell configurations.

The assemblies and structures discussed above may be utilized withinintegrated circuits (with the term “integrated circuit” meaning anelectronic circuit supported by a semiconductor substrate); and may beincorporated into electronic systems. Such electronic systems may beused in, for example, memory modules, device drivers, power modules,communication modems, processor modules, and application-specificmodules, and may include multilayer, multichip modules. The electronicsystems may be any of a broad range of systems, such as, for example,cameras, wireless devices, displays, chip sets, set top boxes, games,lighting, vehicles, clocks, televisions, cell phones, personalcomputers, automobiles, industrial control systems, aircraft, etc.

Unless specified otherwise, the various materials, substances,compositions, etc. described herein may be formed with any suitablemethodologies, either now known or yet to be developed, including, forexample, atomic layer deposition (ALD), chemical vapor deposition (CVD),physical vapor deposition (PVD), etc.

The terms “dielectric” and “insulative” may be utilized to describematerials having insulative electrical properties. The terms areconsidered synonymous in this disclosure. The utilization of the term“dielectric” in some instances, and the term “insulative” (or“electrically insulative”) in other instances, may be to providelanguage variation within this disclosure to simplify antecedent basiswithin the claims that follow, and is not utilized to indicate anysignificant chemical or electrical differences.

The particular orientation of the various embodiments in the drawings isfor illustrative purposes only, and the embodiments may be rotatedrelative to the shown orientations in some applications. Thedescriptions provided herein, and the claims that follow, pertain to anystructures that have the described relationships between variousfeatures, regardless of whether the structures are in the particularorientation of the drawings, or are rotated relative to suchorientation.

The cross-sectional views of the accompanying illustrations only showfeatures within the planes of the cross-sections, and do not showmaterials behind the planes of the cross-sections, unless indicatedotherwise, in order to simplify the drawings.

When a structure is referred to above as being “on”, “adjacent” or“against” another structure, it can be directly on the other structureor intervening structures may also be present. In contrast, when astructure is referred to as being “directly on”, “directly adjacent” or“directly against” another structure, there are no interveningstructures present. The terms “directly under”, “directly over”, etc.,do not indicate direct physical contact (unless expressly statedotherwise), but instead indicate upright alignment.

Structures (e.g., layers, materials, etc.) may be referred to as“extending vertically” to indicate that the structures generally extendupwardly from an underlying base (e.g., substrate). Thevertically-extending structures may extend substantially orthogonallyrelative to an upper surface of the base, or not.

Some embodiments include a memory array having a vertical stack ofalternating insulative levels and wordline levels. Channel materialextends vertically along the stack. Conductive segments are along thewordline levels. Individual of the conductive segments has, along across-section, first and second ends in opposing relation to oneanother. The conductive segments include gates and wordlines adjacentthe gates. The wordlines encompass the second ends, and the gates havesubstantially parabolic noses which encompass the first ends. Memorycell structures are along the wordline levels and are located betweenthe channel material and the parabolic noses of the gates. The memorycell structures include charge-storage regions and charge-blockingregions. The charge-blocking regions are being between thecharge-storage regions and the gates.

Some embodiments include a method of forming an assembly. A firstopening is formed through a stack of alternating first and secondlevels. The first levels comprise a first material, and the secondlevels comprise an insulative second material. The first levels compriseedges along the first opening. The edges of the first levels arerounded, and charge-blocking material is formed adjacent the roundededges. Charge-storage material is formed adjacent the charge-blockingmaterial. Tunneling material is formed adjacent the charge-storagematerial. Channel material is formed within the first opening andadjacent the tunneling material. A second opening is formed through thestack. After the second opening is formed, the first material of thefirst levels is removed to form cavities. Conductive segments are formedwithin the cavities. Each of the conductive segments has, along across-section, first and second ends in opposing relation to oneanother. The conductive segments comprise gates, and comprise wordlinesadjacent the gates. The wordlines encompass the second ends. The gateshave rounded noses encompassing the first ends. The rounded noses arepatterned by the rounded edges of the first levels.

Some embodiments include a method of forming an assembly. A firstopening is formed through a stack of alternating first and secondlevels. The first levels comprise silicon nitride, and the second levelscomprise silicon dioxide. The first levels comprise edges along thefirst opening. The edges of the first level are rounded. Charge-blockingmaterial is formed adjacent the rounded edges. The charge-blockingmaterial has an inner surface which is substantially conformal to therounded edges. Charge-storage material is formed adjacent thecharge-blocking material. Tunneling material is formed adjacent thecharge-storage material. Channel material is formed within the firstopening and adjacent the tunneling material. A second opening is formedthrough the stack. The silicon nitride of the first levels is removed toform cavities. Conductive segments are formed within the cavities. Eachof the conductive segments has, along a cross-section, first and secondends in opposing relation to one another. The conductive segmentscomprise gates, and comprise wordlines adjacent the gates. the wordlinesencompass the second ends. The gates have rounded noses encompassing thefirst ends. The rounded noses are molded by the inner surface of thecharge-blocking material.

In compliance with the statute, the subject matter disclosed herein hasbeen described in language more or less specific as to structural andmethodical features. It is to be understood, however, that the claimsare not limited to the specific features shown and described, since themeans herein disclosed comprise example embodiments. The claims are thusto be afforded full scope as literally worded, and to be appropriatelyinterpreted in accordance with the doctrine of equivalents.

We claim:
 1. A method of forming an assembly, comprising: forming afirst opening through a stack of alternating first and second levels;the first levels comprising a first material, and the second levelscomprising an insulative second material; the first levels comprisingedges along the first opening; rounding the edges of the first levelsand forming charge-blocking material adjacent the rounded edges; formingcharge-storage material adjacent the charge-blocking material; formingtunneling material adjacent the charge-storage material; and formingchannel material within the first opening and adjacent the tunnelingmaterial.
 2. The method of claim 1 wherein the opening is a firstopening, and further comprising forming a second opening through thestack; and after forming the second opening, removing the first materialof the first levels to form cavities.
 3. The method of claim 2, furthercomprising forming conductive segments within the cavities, each of theconductive segments having gate regions having a rounded edge.
 4. Themethod of claim 1 wherein the edges of the first levels are first edges;wherein the second levels have second edges along the opening; whereinthe forming of the rounded edges of the first levels insets the secondedges of the second levels to leave recesses between vertically-adjacentrounded edges of the first levels; and comprising forming an insulativethird material within the recesses prior to forming the charge-blockingmaterial.
 5. The method of claim 4 wherein the second levels havethicknesses of a first dimension; and wherein the recesses have depthsof a second dimension, with the second dimension at least about one-halfof the first dimension.
 6. The method of claim 1 wherein the firstmaterial comprises silicon nitride, and wherein at least some of thecharge-blocking material comprises silicon oxynitride formed byoxidizing the rounded edges of the first levels.
 7. The method of claim1 wherein the rounded noses are substantially parabolic.